1. Field of the Invention
The present invention relates generally to methods and apparatus for making fluid delivery devices for infusing medicinal agents into an ambulatory patient at specific rates over extended periods of time. More particularly, the invention concerns a novel method and apparatus for the large volume manufacture of small, disposable fluid delivery devices for infusion of medicinal agents into a ambulatory patient.
2. Discussion of the Prior Art
Many medicinal agents require an intravenous route for administration thus bypassing the digestive system and precluding degradation by the catalytic enzymes in the digestive tract and liver. The use of more potent medications at elevated concentrations has also increased the need for accuracy in controlling the delivery of such drugs. The delivery device, while not an active pharmacologic agent, may enhance the activity of the drug by mediating its therapeutic effectiveness. Certain classes of new pharmacologic agents possess a very narrow range of therapeutic effectiveness, for instance, too small a dose results in no effect, while too great a dose results in toxic reaction.
In the past, prolonged infusion of fluids has generally been accomplished using gravity flow methods, which typically involve the use of intravenous administration sets and the familiar bottle suspended above the patient. Such methods are cumbersome, imprecise and require bed confinement of the patient. Periodic monitoring of the apparatus by the nurse or doctor is required to detect malfunctions of the infusion apparatus.
The fluid delivery devices made in accordance with the method of the present invention overcome many of the drawbacks of the prior art by making use of advanced types of prestressed elastomeric films which, in cooperation with a base, define a fluid chamber that contains the fluid which is to be dispensed. The prestressed elastomeric film membrane, which is further distended during the filling of the fluid chamber, controllably forces fluid within the chamber outwardly of the device as the membrane moves toward its less distended stating configuration.
The elastomeric film materials used in the fluid delivery devices manufactured in accordance with the methods of the present invention, as well as various alternate constructions of the fluid delivery devices themselves, are described in detail in U.S. Pat. No. 5,205,820 issued to the present inventor. Therefore, U.S. Pat. No. 5,205,820 is hereby incorporated by reference in its entirety as though fully set forth herein. Co-pending U.S. Ser. No. 08/451,520 filed by the present inventor on May 26, 1995 U.S. Pat. No. 5,656,032 also describes several alternate constructions of fluid delivery devices that can be manufactured in accordance with the teachings of the present invention. This co-pending application, which also discloses an apparatus for making fluid delivery devices on an individual basis, is also hereby incorporated by reference in its entirety as though fully set forth herein.
As will be better appreciated from the discussion which follows, the methods and apparatus of the present invention are ideally suited for the large-scale manufacture of fluid delivery devices of the character described herein and in application Ser. No. 08/451,520 U.S. Pat. No. 5,656,032. These delivery devices typically comprise a base assembly and a stored energy means provided in the form of a thin, prestressed, distendable, elastomeric membrane which after being cut in a manner described in Ser. No. 08/451,520 U.S. Pat. No. 5,656,032, cooperates with the base assembly to form a fluid reservoir. Contained within a cavity formed in the base assembly is circuitously shaped, hollow cannula which includes an inlet in communication with the fluid reservoir and an outlet formed in a needle-like segment, which extends generally perpendicularly downward from the lower surface of the base assembly for subdermal infusion of medicinal fluids into the patient.
The novel fluid delivery devices manufactured in accordance with the present invention have an extremely low profile and are eminently capable of meeting the most stringent of fluid delivery tolerance requirements. The devices are small, easy to use and, in accordance with the method of the present invention, can be manufactured in very large quantities at low cost.